The Loeber Risk Score (LRS)was developed to predict early-onset cannabis use in adolescence from late childhood,facilitating early identification. Authors validated the LRS in a diverse,nationwide cohort (N = 4,898)weighted to the composition of the U.S. Census. Participants in 20 cities completed assessments when youth were approximately 5,9,and 15 years old. Parents completed the LRS at the age ?5 and ?9 interviews. At the age ?15 interview,youth reported on the onset of alcohol/drug use before age 15,monthly drinking/binge drinking at ages 14-16,and use of cannabis multiple times per month at ages 14-16.